Adsorbent for an Oral Administration, and Agent for Treating or Preventing Renal or Liver Disease

ABSTRACT

An adsorbent for an oral administration, comprising a spherical activated carbon wherein an average particle diameter is 50 to 200 μm, a specific surface area determined by a BET method is 700 m 2 /g or more, and a bulk density is less than 0.54 g/mL is disclosed. The adsorbent for an oral administration has a high adsorbability, and is capable of adsorbing a large amount of toxins during a retention period in an intestine, and of remarkably increasing an adsorption amount of compounds having a large molecular weight.

TECHNICAL FIELD

The present invention relates to an adsorbent for an oral administrationcomprising a spherical activated carbon having a small average particlediameter and a small bulk density. Further, the present inventionrelates to an agent for treating or preventing a renal or liver disease,comprising the adsorbent for an oral administration as an effectivecomponent.

The adsorbent for an oral administration, according to the presentinvention, exhibits a high adsorbability of indole which is a precursorof indoxyl sulfuric acid attracting attention as a harmful toxin in abody, and therefore, can adsorb many toxins within a given period oftime in which toxins must be adsorbed, during a retention period fromthe oral administration to an excretion.

BACKGROUND ART

In patients suffering a lack of a renal function or a liver function,harmful toxic substances are accumulated or formed in bodies, such asblood, with a progress of a disorder of the organ functions, and thus anencephalopathia occurs, such as a disturbance of consciousness oruremia. Yearly, there is a growing number of such patients, andtherefore, the development of an organ-substitute apparatus ormedicament having a function to remove toxic substances from bodies, inplace of such defective organs, has become a serious problem. A methodfor removing toxic substances by hemodialysis as an artificial kidney isprevalent. Nevertheless, the hemodialysis-based artificial kidneyrequires a special apparatus, and thus, a skilled specialist is requiredfrom a safe operation standpoint. Further, blood must be taken from apatient's body, and thus, there are disadvantages in that patients mustbear high physical, mental and economic burdens. Accordingly,hemodialysis is not satisfactory.

As a means of remedying the above disadvantages, an oral adsorbent whichcan be orally administered and cure a disorder of renal and liverfunctions was developed and utilized [Patent Reference No. 1]. Theadsorbent disclosed in Patent Reference No. 1 comprises a porousspherical carbonaceous substance having particular functional groups,that is, a spherical activated carbon, having a high safety factor andstable to a body, and having a useful selective adsorbability; that is,an excellent adsorbability of harmful substances in the presence of abile acid in an intestine, and a low adsorbability of useful substancessuch as digestive enzymes in the intestine. For these reasons, the oraladsorbent is widely and clinically used for a patient suffering from adisorder of a liver or renal function, as an adsorbent having few sideeffects such as constipation. The above adsorbent disclosed in PatentReference No. 1 was prepared by forming a spherical activated carbonfrom a pitch such as a petroleum pitch as a carbon source, and thencarrying out an oxidizing treatment and a reducing treatment.

Further, an adsorbent for an oral administration providing animprovement in the above useful selective adsorbability, that is, anexcellent adsorbability of harmful substances and a low adsorbability ofuseful substances in the intestine, is known (Patent Reference No. 2).The adsorbent for an oral administration disclosed in Patent ReferenceNo. 2 is based on a finding that the above selective adsorbability isimproved within a special range of a pore volume, that is, when a volumeof pores having a pore diameter of 20 to 15000 nm is from not less than0.04 mL/g to less than 0.10 mL/g. The adsorbent for an oraladministration is very effective in treating diseases where a sufficientadsorption of toxins and a reduced adsorption of useful substances inthe intestine are desired.

Further, a medical adsorbent composed of an activated carbon having aspecific surface area of 500 to 2000 m²/g, a pore volume of 0.2 to 1.0mL/g, and a bulk density of 0.5 to 0.75 g/mL, and prepared bycarbonizing and activating spherical phenol resin is known (PatentReference No. 3). Patent Reference No. 3 mentions that the medicaladsorbent disclosed therein is composed of the activated carbon havingcontrolled properties of the specific surface area, the pore volume, theaverage pore diameter, the particle size, and the amount of oxides onthe surface, and thus, can selectively adsorb ionic organic compoundswhile inhibiting the adsorption of polymers, such as polysaccharides orenzymes, necessary for a body.

It is known that, in a patient suffering from chronic renal failure, aconcentration of indoxyl sulfuric acid in serum may be increased about60 times higher than that in a healthy person, and that a concentrationof indoxyl sulfuric acid in serum can be lowered, and thus, the progressof the chronic renal failure can be delayed by an administration of theoral adsorbent disclosed in the above Patent Reference No. 1 (Non-patentReference Nos. 1 and 2). The mechanism whereby a concentration ofindoxyl sulfuric acid is increased in a patient suffering from chronicrenal failure is assumed as follows. That is, a part of tryptophanderived from proteins is metabolized to indole by Escherichia coli orthe like in an intestinal tract. The indole is taken up, and convertedby a sulfate conjugation to indoxyl sulfuric acid in a liver. Theproduced indoxyl sulfuric acid is excreted from a kidney of a healthyperson. However, the excretory pathway is inhibited in a patientsuffering from chronic renal failure, and thus, indoxyl sulfuric acid isaccumulated in blood.

[Patent Reference No. 1]

Japanese Examined Patent Publication (Kokoku) No. 62-11611

[Patent Reference No. 2]

Japanese Patent No. 3522708 (Japanese Unexamined Patent Publication(Kokai) No. 2002-308785)

[Patent Reference No. 3]

Japanese Unexamined Patent Publication (Kokai) No. 2004-24414

[Non-patent Reference No. 1]

Nichijin-shi (The Japanese journal of nephrology), vol. 32, No. 6, 1990,pp 65-71

[Non-patent Reference No. 2]

Rinsho-Toseki (The Japanese Journal of Clinical Dialysis), vol. 14, No.4, 1998, pp 433-438

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The above selective adsorbability is a very important property of theoral adsorbent composed of the spherical activated carbon. On the otherhand, it is also very important to adsorb and remove as many as possibleof toxins in a body, and as soon as possible. In general, the oraladsorbent has a retention period of about 3 to 5 hours in an upperportion of a small intestine. Therefore, a spherical activated carbonhaving a high adsorbability for a period of about 3 hours aftercontacting toxins, and an excellent initial adsorbability, is desirable.

As shown in Examples below, however, the oral adsorbents disclosed inPatent References No. 1 and No. 2 do not have a high adsorbability forabout 3 hours after contacting toxins, and are conveyed to a lowerportion of a small intestine and a large intestine, and then excretedoutside of a body, while the adsorbability is not completely exhausted,but enough adsorbability is maintained.

Therefore, the inventors of the present invention engaged in intensiveresearch to develop an oral adsorbent having a high adsorbability, thatis, an oral adsorbent capable of adsorbing and removing a large amountof toxins, and having an excellent initial adsorption rate, and foundthat an oral adsorbent having an excellent adsorbability and anexcellent initial adsorption rate can be obtained in an average particlediameter, that is, in a small average particle diameter, different fromthat of the conventionally known oral adsorbents disclosed in PatentReferences No. 1 and No. 2. Further, it is surprisingly found that aspherical activated carbon before particular functional groups areapplied has the above excellent properties. The activated carbon foundby the inventors can adsorb a large amount of toxins, particularlyindole, for about 3 hours during the retention period in the upperportion of a small intestine, and thus, it becomes possible to reduce adosage.

Further, the inventors of the present invention found that, even in theabove range of the average particle diameter found by the inventors ofthe present invention, that is, in the above range of the small averageparticle diameter, an adsorbed amount of tryptophan or tryptamine havinga molecular weight larger than that of indole is remarkably increased,in a bulk density range (i.e., a low bulk density range) different fromthat of the activated carbon disclosed in Patent Reference No. 3.

The present invention is based on the above findings.

Means for Solving the Problems

Accordingly, the present invention relates to an adsorbent for an oraladministration, comprising a spherical activated carbon wherein anaverage particle diameter is 50 to 200 μm, a specific surface areadetermined by a BET method is 700 m²/g or more, and a bulk density isless than 0.54 g/mL.

Further, the present invention relates to an agent for treating orpreventing a renal or liver disease, comprising the adsorbent for anoral administration as an effective component.

EFFECTS OF THE INVENTION

The adsorbent for an oral administration of the present invention has ahigh adsorbability, and thus an excellent initial adsorbability.Therefore, the oral adsorbent of the present invention can very rapidlyadsorb harmful toxins in a body during the general retention period inan upper portion of a small intestine, and is efficient as an agent fortreating or preventing a renal or liver disease. Further, a dosage canbe reduced in comparison with that of a conventional oral adsorbent.

Further, the adsorbent of the present invention has a small averageparticle diameter, and thus, an unpleasant granular feeling when takeninto a mouth is eliminated or reduced, whereby the adsorbent can beeasily administered. In addition, the inventors of the present inventioncarried out abdominal surgery of rats to which the adsorbent of thepresent invention was administered, and confirmed that the attachment ofthe adsorbent to an inner surface of the intestine was rarely observed,and in some cases, the amount of the adsorbents attached to the innersurface of the intestine became smaller than that of the conventionaladsorbents having a larger average particle diameter, such as the oraladsorbent disclosed in Patent Reference No. 1. That is, the adsorbent ofthe present invention is at least comparable to the conventional oraladsorbents with respect to the attachment to the inner surface of theintestine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an electron microscope photograph of the spherical activatedcarbon according to the present invention prepared in Example 1.

FIG. 2 is a graph showing a variation in adsorbing rates when a shakingtime varies, for the spherical activated carbon prepared in Example 1,and Comparative Examples 1 and 2.

FIG. 3 is a graph showing the relationship between the average particlediameter of the spherical activated carbon and the amount of indoleadsorbed by the spherical activated carbon.

BEST MODE FOR CARRYING OUT THE INVENTION

A spherical activated carbon used as the adsorbent for an oraladministration according to the present invention means anon-surface-modified spherical activated carbon. Thenon-surface-modified spherical activated carbon as used herein means aspherical activated carbon having a total acidic-group amount of lessthan 0.30 meq/g. On the other hand, a surface-modified sphericalactivated carbon means a spherical activated carbon having a totalacidic-group amount of 0.30 meq/g or more. As mentioned below, thenon-surface-modified spherical activated carbon is a porous materialprepared, for example, by heat-treating a carbonaceous precursor, andactivating the resulting product, that is, an activated carbon without asubsequent surface-modification by oxidizing and reducing treatments, oran activated carbon prepared by a heat-treatment at a non-oxidizingatmosphere after the activating treatment as above. On the other hand,the surface-modified spherical activated carbon is a porous materialprepared by heat-treating a carbonaceous precursor, activating theresulting product, and subsequently, carrying out a surface-modificationby oxidizing and reducing treatments. The surface-modified sphericalactivated carbon can exhibit a moderate interaction with acids andbases. The total acidic-group amount of the non-surface-modifiedspherical activated carbon is preferably 0.25 meq/g or less, morepreferably 0.20 meq/g or less.

The spherical activated carbon used as the adsorbent for an oraladministration according to the present invention has a specified rangeof the average particle diameter and a specified range of the bulkdensity, as mentioned above. The average particle diameter is 50 to 200μm, preferably 50 to 180 μm, more preferably 50 to 150 μm. The wording“average particle diameter” (Dv50) as used herein means a particle sizeat the particle size cumulative percentage of 50% in a particle sizecumulative diagram based on a volume. The bulk density is less than 0.54g/mL. The upper limit of the bulk density is preferably 0.50 g/mL (thatis, not more than 0.50 g/mL, or less than 0.50 g/mL), more preferably0.49/mL. There is no lower limit to the bulk density, but it ispreferably 0.30 g/mL. The term “bulk density” (ρ_(B)) as used hereinmeans a value obtained by dividing a dry weight, W(g), of sphericalactivated carbons filled in a vessel by a volume, V (mL), of thespherical activated carbons filled in the vessel, and can be calculatedfrom the following equation:ρ_(B)(g/mL)=W(g)/V(mL)  [Formula 1]

To the best of the knowledge of the inventors of the present invention,a spherical activated carbon having an average particle diameter of 50to 200 μm is not known in the field of a spherical activated carbon usedas an adsorbent for an oral administration. For example, all the averageparticle diameters of the porous spherical carbonaceous substanceconcretely prepared in Examples 1 to 5 of Patent Reference No. 2 are 350μm. In this connection, Patent Reference No. 2 generally discloses theporous spherical carbonaceous substance having a diameter of 0.01 to 1mm, i.e., 10 to 1000 μm (see for example, claim 1). However, the rangeof 0.01 to 1 mm is described as a “diameter”, not as an average particlediameter. Further, as mentioned above, the adsorbents concretelydisclosed in Examples 1 to 5 of Patent Reference No. 2 are only theporous spherical carbonaceous substances having an average particlediameter of 350 μm, and Patent Reference No. 2 does not disclose that aspherical activated carbon having an average particle diameter of 50 to200 μm exhibits an increased adsorbing amount and an enhanced initialadsorbing rate. In this connection, in Comparative Examples of PatentReference No. 2, the carbonaceous substance having an average particlediameter of 20 μm (Comparative Example 3) and the carbonaceous substancehaving an average particle diameter of 40 μm (Comparative Example 6) aredisclosed. However, the carbonaceous substance having an averageparticle diameter of 20 μm (Comparative Example 3) was a productobtained by grinding the porous spherical carbonaceous substanceprepared in Example 1 by a grinder, and it was not spherical. Thecarbonaceous substance having an average particle diameter of 40 μm(Comparative Example 6) is a powdery active charcoal for a medical use.

Further, Patent Reference No. 1 generally discloses a sphericalcarbonaceous substance having a diameter of 0.05 to 1 mm, 50 to 1000 μm,(see, for example, claim 1), and concretely discloses carbonaceoussubstances having a particle diameter of 0.05 to 1 mm, or 0.07 to 1 mmin Examples 1 to 3. However, it is apparent that the particle diametersin Patent Reference No. 1 are not average particle diameters, and itappears to be a range from the minimum particle diameter to the maximumparticle diameter.

A technology for producing porous spherical carbonaceous substanceshaving various properties described in Patent References No. 1 and No. 2has rapidly been developed. As shown in Examples mentioned below, aproduction of the porous spherical carbonaceous substances havingvarious desired propertied has become easier, for example, usingsynthetic resin as a carbon source. For example, the average particlediameter can be relatively easily controlled. On the contrary, when apitch is used as a carbon source, it is still not necessarily easy intechnical terms to produce spherical activated carbons having, forexample, an average particle diameter of 50 to 200 μm. At least, withouta motivation to produce the spherical activated carbon having an averageparticle diameter of 50 to 200 μm, it would be unthinkable to producethe same. Therefore, at least at the time when Patent Reference No. 1was filed, it was unthinkable to produce spherical activated carbonshaving an average particle diameter of 50 to 200 μm from a pitch.

As above, the spherical activated carbon used as the adsorbent for anoral administration according to the present invention is a sphericalactivated carbon having a specific range of an average particle diameter(50 to 200 μm). The average particle diameter in the present inventionis smaller than the average particle diameter (350 μm) of the porousspherical carbonaceous substance concretely disclosed in PatentReference No. 2. Further, the spherical activated carbon used as theadsorbent for an oral administration according to the present inventionis characterized by a higher adsorbability and an excellent initialadsorbability, in comparison with the conventional spherical activatedcarbon. However, a decrease of the average particle diameter to such anextent does not provide a substantial increase of a specific surfacearea (outer surface area). The substantial improvement in theadsorbability of the spherical activated carbon used in the presentinvention cannot be explained only from the viewpoint of the increase ofthe specific surface area, i.e., the outer surface area.

Incidentally, the specific surface areas (outer surface areas) of 1 g ofthe spherical activated carbon having an average particle diameter of350 μm and 1 g of the spherical activated carbon having an averageparticle diameter of 50 μm will be calculated. When the density of thespherical activated carbon is ρ(g/m³), and the particle diameter isd(m), the outer surface area (S) per 1 g of the spherical activatedcarbon can be calculated by the equation:S=32/3ρd.  [equation 2]When the density (ρ) of the spherical activated carbon is 1×10⁶ g/m³ (1g/cm³), and the particle diameter (d) is 350×10⁻⁶ m (350 μm), the outersurface area (S) is 0.03 m²/g. Similarly, when the particle diameter (d)is 50×10⁻⁶ m (50 μm), the outer surface area (S) is 0.21 m²/g. Thedifference therebetween is 0.18 m²/g. The specific surface area of thespherical activated carbon according to the present invention is 700m²/g, and thus, an outer surface area increase derived from the decreaseof the particle diameter is less than 0.1% in the whole specific surfacearea.

The spherical activated carbon used as the adsorbent for an oraladministration according to the present invention preferably has anarrow size distribution. For example, when a length average particlediameter of a number-based-average is D₁(=ΣnD/Σn), and a weight averageparticle diameter of a weight-based-distribution is D₄(=Σ(nD⁴)/Σ(nD³)),the ratio (D₄/D₁) of the spherical activated carbon used as theadsorbent for an oral administration according to the present inventionis preferably 3 or less, more preferably 2 or less, particularlypreferably 1.5 or less. This means that the nearer the above ratio(D₄/D₁) is to 1, the narrower the size distribution. In the aboveequation, D is a representative particle diameter in a fraction of theparticle diameters measured, and n is the number of particles.

The spherical activated carbons having an average particle diameter of50 to 200 μm are disclosed in Examples of Patent Reference No. 3.However, Patent Reference No. 3 generally defines the average particlediameter as 350 μm or less, but does not disclose that particularlyadvantageous effects can be obtained when the average particle diameteris 200 μm or less, or that a spherical activated carbon having anaverage particle diameter of 50 to 200 μm exhibits an excellent initialadsorbability. As above, in Examples of Patent Reference No. 3, only thespherical activated carbons having an average particle diameter of 60 to117 μm are produced. Further, the range of the bulk density of thespherical activated carbons concretely produced in Examples of PatentReference No. 3 is from 0.54 to 0.61 g/mL. In addition, Patent ReferenceNo. 3 explicitly mentions that when the bulk density (packing density)is 0.5 g/mL or less, pore diameters of the activated carbons becomelarger, high molecular compounds, for example, proteins (enzymes) suchas trypsin or polysaccharides such as pullulan might be adsorbed, andthus a dosage becomes unfavorably larger. Therefore, Patent ReferenceNo. 3 does not disclose a spherical activated carbon having a bulkdensity of less than 0.54 g/mL, or at least does not disclose aspherical activated carbon having a bulk density of 0.50 g/mL or less,or less than 0.50 g/mL.

A bulk density is a good index showing the degree of the activation, fora surface-modified spherical activated carbon or a spherical activatedcarbon. This means that the smaller the bulk density, the more theactivation proceeds. In the process for producing the surface-modifiedspherical activated carbon or the spherical activated carbon, relativelysmall pores are formed in the initial stage of the activation with steamas mentioned below, and then, as the activation proceeds, the pore sizesare enlarged and thus, the bulk density is lowered.

The reason that the adsorbent for an oral administration according tothe present invention exhibits excellent effects as mentioned above hasnot been elucidated at the present time, but can be presumed as follows.However, the present invention is not limited by the presumption givenbelow:

Proteins and amino acids are taken into a person as essential nutrients.However, the necessary amount greatly exceeds the amount required togrow and maintain constitutional components for a body, and as a result,the taken nitrogen compounds are degraded and eliminated from a wholebody. If a liver function or a renal function is damaged, the nitrogencompounds are insufficiently metabolized and eliminated, and thus,accumulated in a body to become uremic substances. Therefore, it ispreferable that the adsorbent has properties to adsorb various moleculeshaving a broad spectrum of molecular weights from several tens toseveral hundred, so as to enhance the adsorbability of the oraladsorbent for adsorbing uremic substances. The adsorbent for an oraladministration according to the present invention has a small particlediameter and an increased outer surface area, whereby an area where theuremic molecules are brought into contact with the adsorbent for an oraladministration is increased. Further, the adsorbent for an oraladministration according to the present invention has a small particlediameter and thus, the mean free path becomes shorter when the uremicsubstances are diffused into the particle of the oral adsorbents,whereby an adsorbing rate becomes faster. As the bulk density is low andthe pore size is enlarged, relatively large molecules can be adsorbed.Accordingly, compounds having a wide spectrum of molecular weights canbe adsorbed.

A carbon source for the spherical activated carbon used as the adsorbentfor an oral administration of the present invention may be anycarbon-containing material. The carbon-containing material which may beused is, for example, a synthetic resin or pitch. A heat-fusible resinor a heat-infusible resin can be used as the synthetic resin. The term“heat-fusible resin” as used herein means a resin from which anactivated carbon cannot be produced because it is melted and decomposedas a temperature is raised, if an activation treatment is carried outbefore a treatment to impart infusibility. However, when theheat-fusible resin is treated to impart infusibility in advance, andthen is activated, an activated carbon can be produced therefrom. On thecontrary, the heat-infusible resin means a resin from which an activatedcarbon can be produced by the proceeding of carbonization withoutmelting as a temperature is raised, even if a treatment to impartinfusibility is not carried out in advance. The treatment to impartinfusibility is, for example, an oxidation treatment carried out at 150°C. to 400° C. under an atmosphere containing oxygen, as mentioned below.

A typical example of the heat-fusible resin is a thermoplastic resin,such as a cross-linked vinyl resin. A typical example of theheat-infusible resin is a thermosetting resin, such as a phenol or furanresin. Any known thermoplastic or thermosetting resin from which aspherical shape is formed can be used. When the surface-modifiedspherical activated carbon is produced from the cross-linked vinylresin, the above treatment to impart infusibility is necessary. On theother hand, the above treatment to impart infusibility is not necessarywhen the spherical activated carbon is produced from an ion-exchangeresin prepared by applying functional groups to the cross-linked vinylresin. It is believed that the cross-linked resin is modified from theheat-fusible resin to the heat-infusible resin by the treatment used tointroduce the functional groups thereto, and the functional groupsintroduced thereby. That is, the cross-linked vinyl resin belongs to theheat-fusible resin as used herein, whereas the ion-exchange resinbelongs to the heat-infusible resin as used herein.

As a carbon source in the present invention, an ion-exchange resin, across-linked vinyl resin, or pitch is preferably used, and anion-exchange resin or a cross-linked vinyl resin is more preferablyused.

When the heat-infusible resin such as an ion-exchange resin is used as acarbon source for the preparation of the spherical activated carbon usedas the adsorbent for an oral administration of the present invention, amethod substantially the same as a conventional method for productionfrom pitch can be used. For example, a spherical material of aheat-infusible resin is initially activated at 700 to 1000° C. in a gasstream reactive with carbon (for example, steam or carbon dioxide gas)to obtain the spherical activated carbon. The term “activated carbon” asused herein means a porous product prepared by a heat-treatment of acarbon precursor such as a spherical heat-infusible resin, and asubsequent activation, and the term “spherical activated carbon” as usedherein means an activated carbon having a spherical shape and a specificsurface area of 100 m²/g or more. In the present invention, thespherical activated carbon having a specific surface area of 700 m²/g ormore, more preferably 1300 m²/g or more, particularly preferably 1650m²/g or more is used. An average particle diameter of the sphericalheat-infusible resin used as a starting material is preferably about 70to 500 μm, more preferably 10 to 300 μm.

When the heat-fusible resin such as a cross-linked vinyl resin is usedas a carbon source, the spherical material of a heat-fusible resin issoftened by the heat-treatment and changed to an aspherical shape, orfused together by the heat-treatment. The softening can be inhibited byan oxidation at 150° C. to 400° C. in an atmosphere containing oxygen,as a treatment to impart infusibility before the activation as above.

Further, if many pyrolysis gases or the like are generated by theheat-treatment of the spherical heat-fusible resin which has beentreated to impart infusibility or the spherical heat-infusible resin,pyrolysis products may be removed in advance by carrying out apre-calcination, prior to the activation.

When pitch is used as a carbon source for the production of thespherical activated carbon used as the adsorbent for an oraladministration of the present invention, the spherical activated carbonhaving an average particle diameter of 50 to 200 μm can be prepared bythe following methods.

A dicyclic or tricyclic aromatic compound having a boiling point of 200°C. or more or a mixture thereof is added as an additive to a pitch suchas a petroleum pitch or a coal pitch. The whole is heated and mixed, andthen shaped to obtain a shaped pitch. The size of the shaped pitch canbe controlled by a nozzle size used in an extrusion molding, or crushingconditions of the shaped pitch. The smaller the volume of the shapedpitch, the smaller the spherical pitch which may be produced, and thus,the smaller the particle diameter of the spherical activated carbonwhich may be produced.

Then, the shaped pitch is dispersed and granulated in hot water at 50°C. to 120° C., with stirring, to obtain a microspherical shaped pitch.The microspherical shaped pitch is cooled to obtain a spherically shapedpitch. The average particle diameter of the spherically shaped pitch ispreferably 60 to 350 μm, more preferably 60 to 300 μm. Further, theadditive is extracted and removed from the spherically shaped pitch by asolvent having a low solubility to the pitch but a high solubility tothe additive, to thereby obtain a porous pitch. The porous pitch isoxidized with an oxidizing agent to be an infusible porous pitch.Further, the resulting heat-infusible porous pitch is treated at 800 to1000° C. with a gas stream reactive with carbon (for example, steam orcarbon dioxide gas) to obtain a spherical activated carbon.

The purpose of the addition of the aromatic compound as above is thatthe porous pitch is produced by extracting and removing the additivefrom the shaped pitch, whereby a structure control and a calcination ofthe carbonaceous material by oxidization in the subsequent steps is madeeasier. As the additive, for example, naphthalene, methylnaphthalene,phenyl-naphthalene, benzyl-naphthalene, methylanthracene, phenanthrene,or biphenyl may be used alone or in a mixture thereof. An amount of theadditive added to the pitch is preferably 10 to 50 parts by weight ofthe aromatic compound with respect to 100 parts by weight of the pitch.

The pitch and the additive are mixed under a melted condition withheating, to achieve a homogeneous mixing. The shaping may be conductedduring the melted condition, or by grinding the mixture after cooling.However, a method comprising filamentously extruding a mixed pitch undermelted condition, and then, cutting the extruded product into an equallylength or crushing the extruded product is preferable, because adistribution of the particle diameter can be controlled in a narrowerrange. The particle diameter may be controlled by the nozzle diameterused in the extrusion of the mixed pitch. A thin nozzle can be used toobtain the smaller shaped mixed pitch.

A preferable solvent used to extract and remove the additive from themixture of the pitch and the additive may be, for example, an aliphatichydrocarbon, such as butane, pentane, hexane, or heptane, a mixturecomprising an aliphatic hydrocarbon as a main component, such as naphthaor kerosene, or an aliphatic alcohol, such as methanol, ethanol,propanol, or butanol.

The additive may be removed from the shaped mixture by extracting theadditive with the solvent from the shaped mixture of the pitch and theadditive, while maintaining the shape. It is assumed that, upon theextraction, through-holes of the additive are formed in the shapedproduct, and a shaped pitch having a uniform porosity can be obtained.

Then, the resulting shaped porous pitch is treated to impartinfusibility, that is, oxidized with an oxidizing agent, preferably at150° C. to 400° C. to obtain the shaped porous infusible pitch having anon-fusibility to heat. As the oxidizing agent, for example, oxygen gas(O₂), or a gas mixture prepared by diluting oxygen gas (O₂) with air,nitrogen or the like may be used.

When pitch is used as a carbon source for the production of thespherical activated carbon used as the adsorbent for an oraladministration of the present invention, the pore volume can becontrolled by controlling an amount or a kind of the aromatic compoundadded, or precipitation conditions in the pitch.

Further, the pore volume can be controlled by activating ametal-containing spherical carbonaceous material. For example, aspherical activated carbon wherein a volume of pores having a porediameter of 7.5 to 15000 nm is 0.25 to 1.0 mL/g can be prepared by thefollowing method.

The metal-containing spherical carbonaceous material can be prepared by,for example, (1) addition to the pitch, (2) impregnation of the porouspitch, (3) impregnation of the porous infusible pitch, (4) impregnationof the spherical carbon prepared by heating the porous infusible pitch,or (5) impregnation of the spherical activated carbon prepared byactivation. The addition of a metallic compound or the impregnation witha metallic compound can be carried out by dissolving the metalliccompound in a solvent, to prepare a metallic compound solution, addingthe solution to a carbon precursor or impregnating a carbon precursorwith the solution, and heating to evaporate and remove the solvent, tothereby obtain a metal-containing pitch, a metal-containing sphericalporous pitch, a metal-containing spherical porous infusible pitch, or ametal-containing spherical activated carbon, or the like. When themetallic compound is added to the pitch or the spherical porous pitch isimpregnated with the metallic compound, the above spherical activatedcarbon can be obtained by preparing the metal-containing sphericalporous infusible pitch according to the above method; activating at 800°C. to 1000° C. in a gas stream having a reactivity to carbon, such assteam or carbon dioxide gas, or a gas mixture containing the above gasas a main component, to obtain a metal-containing porous sphericalactivated carbon, and washing with an acid to remove the metal. Further,when the spherical activated carbon is impregnated with the metalliccompound, the above spherical activated carbon can be obtained byimpregnating the spherical activated carbon with the metallic compound,carrying out again the activation, and washing with an acid to removethe metal.

Any metal which exhibits a catalytic effect in the steam activation canbe used as the metal for preparing the metal-containing sphericalcarbonaceous material. The preferable metal is, for example, atransition metal, such as cobalt, iron, or nickel, a rare earth metal,such as yttrium, or a compound thereof, or a salt of the compound. Themetallic compound or the salt of the compound may be, for example, aninorganic compound, such as a hydroxide, chloride, nitrate, or sulfate,an organic salt, such as acetylacetone salt or acetate, or anorganic-inorganic complex salt, each containing the metallic element.The metal is introduced into carbon so that a metal atom concentrationin the carbonaceous material before carrying out the activationtreatment ranges preferably from 0.001 to 10% by weight, more preferablyfrom 0.001 to 5% by weight.

The washing treatment is carried out to ensure a sufficient purity ofthe spherical activated carbon from a standpoint of a safe oraladministration. It is necessary to remove a metal content by washingwith water, or an acidic solution of hydrochloric acid, nitric acid,sulfuric acid, or hydrofluoric acid. After washing, the metal content ofthe spherical activated carbon is preferably 150 ppm or less, morepreferably 100 ppm or less, particularly preferably 50 ppm or less.

The resulting spherical activated carbon is oxidized at 300 to 800° C.,preferably 320 to 600° C., in an atmosphere containing 0.1 to 50 vol %,preferably 1 to 30 vol %, particularly preferably 3 to 20 vol % ofoxygen, and then reduced at 800 to 1200° C., preferably 800 to 1000° C.,in an atmosphere of non-oxidative gas, to thereby obtain thesurface-modified spherical activated carbon. The surface-modifiedspherical activated carbon as used herein means a porous materialprepared by oxidizing and reducing the above spherical activated carbon.

In the present invention, however, the spherical activated carbon can beused as the adsorbent for an oral administration, without carrying outthe oxidation and reduction steps for applying functional groups theretoas subsequent processes, that is, in the form of the spherical activatedcarbon.

It is important for the heat-infusible resin used as the startingmaterial that a spherical product can be formed, and it is not fused orsoftened, and the shape is not changed, by a heat-treatment at atemperature of 500° C. or less. A heat-fusible resin can be preferablyused, after being treated to impart infusibility, for example, oxidized,to thereby be converted to a state which can avoid a fusion oxidation.

A resin capable of obtaining a high carbonization yield by aheat-treatment is preferable as the heat-infusible resin used a startingmaterial. If the carbonization yield is low, a strength of the sphericalactivated carbon becomes low. Further, undesirable pores are formed anda bulk density of the spherical activated carbon is lowered, and thus, aspecific surface area per volume is lowered. Therefore, a volume to beorally administered is increased, and thus, a problem arises in that anoral administration becomes difficult. Accordingly, a heat-infusibleresin having a higher carbonization yield is preferable. A yield by aheat-treatment at 800° C. in an atmosphere of non-oxidative gas ispreferably 30% by weight or more, more preferably 35% by weight or more.

An ion-exchange resin is preferable as a heat-infusible resin used as astarting material, because an oral adsorbent having a high adsorbabilityof toxins to be removed can be produced. Generally, an ion-exchangeresin comprises a copolymer (that is, a heat-fusible resin, such as across-linked vinyl resin) of divinylbenzene and styrene, acrylonitrile,acrylic acid, or methacrylic acid, and essentially has a structurewherein ion-exchange groups are bonded to a copolymer matrix having athree-dimensional network skeleton. The ion-exchange resin is generallyclassified, with respect to the kinds of ion-exchange groups, into astrongly acidic ion-exchange resin having sulfonic acid groups, a weaklyacidic ion-exchange resin having carboxylic or sulfonic acid groups, astrongly basic ion-exchange resin having quaternary ammonium salts, anda weakly basic ion-exchange resin having primary or tertiary amines. Inaddition, a so-called hybrid ion-exchange resin having both acidic andbasic ion-exchange groups is included as a special ion-exchange resin.In the present invention, all of the above ion-exchange resins may beused as a starting material.

The spherical activated carbon wherein a volume of pores having a porediameter of 7.5 to 15000 nm is from 0.25 mL/g to 1.0 mL/g can beobtained by carrying out the activating treatment to the heat-infusibleresin, particularly an ion-exchange resin, used as a carbon sourceaccording to the above-mentioned procedure.

A pitch may be used as a starting material. The pitch used as thestarting material preferably has a high carbonization yield obtained bya heat treatment. If the carbonization yield is low, a strength of thespherical activated carbon becomes low. Further, undesirable pores areformed and a bulk density of the spherical activated carbon is lowered,and thus, a specific surface area per volume is lowered. Therefore, avolume to be orally administered is increased, and thus, a problemarises in that an oral administration becomes difficult. Accordingly, apitch having a higher carbonization yield is preferable. A yieldobtained by a heat-treatment at 800° C. in an atmosphere ofnon-oxidative gas is preferably 50% by weight or more, more preferably60% by weight or more.

A cross-linked vinyl resin belonging to the heat-fusible resin issoftened and melted when heated in an atmosphere of non-oxidative gas,and thus, only a carbonization yield of about 10% is obtained at best.However, when the cross-linked vinyl resin is oxidized at 150° C. to400° C. in an atmosphere containing oxygen as a treatment to impartinfusibility, a spherical carbonaceous material with a highcarbonization yield of 30% or more can be obtained without softening ormelting. A spherical activated carbon can be obtained by carrying out anactivation treatment the same as that of the heat-infusible resin.

The cross-linked vinyl resin used as a starting material may be, forexample, a spherical polymer prepared by an emulsion polymerization, abulk polymerization, or a solution polymerization, preferably aspherical polymer prepared by a suspension polymerization. When thespherical cross-linked vinyl resin having a diameter of 50 μm or more istreated to uniformly impart infusibility, pores must be formed inadvance in the cross-linked vinyl resin. The pores can be formed in theresin by adding porogen during the polymerization step. The surface areaof the cross-linked vinyl resin required to uniformly impartinfusibility thereto is preferably 10 m²/g or more, more preferably 50m²/g or more.

For example, when the cross-linked vinyl resin is prepared by asuspension polymerization, an organic phase containing vinyl monomers, across-linking agent, porogen, and a polymerization initiator is added toan aqueous dispersion medium containing a dispersion-stabilizing agent,the whole is mixed with stirring to form many organic droplets suspendedin an aqueous phase, and the monomers in the organic droplets arepolymerized by heating, to thereby prepare the spherical cross-linkedvinyl resin.

As the vinyl-based monomer, any vinyl-based monomer from which aspherical shape can be formed may be used. For example, an aromaticvinyl-based monomer, such as styrene, a styrene derivative wherein ahydrogen atom of a vinyl group or a phenyl group is substituted, or acompound wherein a heterocyclic or polycyclic compound is bonded to avinyl group instead of a phenyl group can be used. An example of thearomatic vinyl-based monomer may be α- or β-methyl styrene, α- orβ-ethyl styrene, methoxy styrene, phenyl styrene, or chlorostyrene, or,o-, m-, or p-methyl styrene, ethyl styrene, methoxy styrene, methylsilylstyrene, hydroxylstyrene, chloro-styrene, cyanostyrene, nitrostyrene,aminostyrene, carboxy-styrene, or sulfoxystyrene, sodium styrenesulfonate, or vinyl pyridine, vinyl thiophene, vinyl pyrrolidone, vinylnaphthalene, vinyl anthracene, or vinylbiphenyl. Further, an aliphaticvinyl-based monomer can be used. For example, there may be mentionedvinyl esters such as ethylene, propylene, isobutylene, diisobutylene,vinyl chloride, acrylate, methacrylate, or vinyl acetate; vinylketonessuch as vinyl methyl ketone, or vinyl ethyl ketone; vinylaldehydes, suchas acrolein, or methacrolein; vinylethers, such as vinylmethylether, orvinylethylether; or vinyl nitriles, such as acrylonitrile, ethylacrylonitrile, diphenyl acrylonitrile, chloroacrylonitrile.

Any cross-linking agent which may be used for the cross-lining of theabove vinyl-based monomer may be used. For example, there may bementioned divinylbenzene, divinyl-pyridine, divinyltoluene,divinylnaphthalene, diallyl phthalate, ethylene glycol diacrylate,ethylene glycol dimethylate, divinylxylene, divinylethylbenzene,divinyl-sulfone, polyvinyl or polyallyl ether of glycol or glycerol,polyvinyl or polyallyl ether of pentaerythritol, polyvinyl or polyallylether of mono or dithio derivative of glycol, polyvinyl or polyallylether of resorcinol, divinyl ketone, divinyl sulfide, allyl acrylate,diallyl maleate, diallyl fumarate, diallyl succinate, diallyl carbonate,diallyl malonate, diallyl oxalate, diallyl adipate, diallyl sebacate,triallyl tricarballylate, triallyl aconitate, triallyl citrate, triallylphosphate, N,N′-methylene diacrylamide,1,2-di(α-methylmethylenesulfoneamido)ethylene, trivinylbenzene,trivinylnaphthalene, polyvinylanthracene, or trivinylcyclohexane. Aparticularly preferable cross-linking agent is polyvinyl aromatichydrocarbon, such as divinylbenzene, glycol trimethacrylate such asethylene glycol dimethacrylate, or polyvinyl hydrocarbon such astrivinyl cyclohexane). Divinylbenzene is most preferable, because of anexcellent property of thermal decomposition.

As an appropriate porogen, there may be mentioned alkanol having 4 to 10carbon atoms, such as, n-butanol, sec-butanol, 2-ethylhexanol, decanol,or 4-methyl 2-pentanol, alkyl ester having at least 7 carbon atoms, suchas n-hexyl acetate, 2-ethylhexyl acetate, methyl oleate, dibutylcebacate, dibutyl adipate, or dibutylcarbonate, alkyl ketone having 4 to10 carbon atoms, such as dibutyl ketone or methyl isobutyl ketone, oralkyl carboxylic acid, such as heptanoic acid, aromatic hydrocarbon,such as toluene, xylene, or benzene, higher saturated aliphatichydrocarbon, such as hexane, heptane, or isooctane, or cyclic aliphatichydrocarbon, such as cyclohexane.

A polymerization initiator is not particularly limited, and an initiatorusually used in this field can be used in the present invention. An oilsoluble initiator which is soluble in a polymerizable monomer ispreferable. As an example of the polymerization initiator, there may bementioned a dialkyl peroxide, a diacyl peroxide, a peroxyester, aperoxydicarbonate, or an azo compound. More particularly, a dialkylperoxide, such as methylethyl-peroxide, di-t-butyl peroxide, or dicumylperoxide; a diacyl peroxide, such as isobutylperoxide, benzoylperoxide,2,4-dichloro-benzoylperoxide, or 3,5,5-trimethylhexanoyl peroxide; aperoxyester, such as t-butylperoxypyvalate, t-hexyl-peroxypyvalate,t-butylperoxyneodecanoate, t-hexylperoxy-neodecanoate, 1-cyclohexyl1-methylethylperoxy-neodecanoate,1,1,3,3-tetramethylbutylperoxyneodecanoate, cumyl peroxy-neodecanoate,or (α,α-bisneodecanoyl peroxy)diisopropyl-benzene; a peroxydicarbonate,such as bis(4-t-butyl-cyclohexyl)peroxy-dicarbonate, di n-propyl-oxydicarbonate, diisopropyl peroxydicarbonate,di(2-ethylethylperoxy)-dicarbonate, dimethoxybutylperoxy-dicarbonate,di(3-methyl 3-methoxybutylperoxy)dicarbonate; or an azo compound, suchas 2,2′-azobisisobutylonitorile,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile,2,2′-azobis(2,4-dimethylvalero-nitrile), or1,1′-azobis(1-cyclohexanecarbonitrile).

When the heat-fusible resin or the heat-infusible resin is used toprepare the spherical activated carbon according to the presentinvention, various properties, such as an average particle diameter, apore volume, a particle size distribution, or a specific surface area,of the spherical activated carbon can be controlled by various methods.For example, the average particle diameter and the particle sizedistribution varies with the size of droplet in an aqueous phase, andthe size of the droplet can be controlled by an amount of a suspendingagent, the number of stirring revolutions, a shape of the stirringblade, or a monomer ratio in an aqueous phase, that is, a ratio of anamount of water and an amount of monomers. For example, the size of thedroplet can be lowered by increasing an amount of a suspending agent, orincreasing the number of stirring revolutions. Further, it is preferableto decrease an amount of monomers in an aqueous phase, not only becausean aggregation of droplets can be controlled, but also because a heat ofpolymerization can be easily removed. However, it is not preferable, inview of productivity, that an amount of monomer ratio is too low,because an amount of monomers per a batch, and thus, an amount ofsynthetic resin produced is decreased.

When the controlled pore diameter is 10 nm or more, the pore volume andthe specific surface area can be controlled mainly by an amount and akind of porogen. When the controlled pore diameter is 10 nm or less, thepore volume and the specific surface area can be controlled byconditions of steam activation. In addition, the microtexture as thespherical activated carbon can be controlled by a kind of a resin, akind and an amount of a cross-linking agent, conditions for impartinginfusibility, and/or activating temperature, or the like.

In the spherical activated carbon used as the adsorbent for an oraladministration of the present invention, a specific surface area(referred to as “SSA” hereinafter) determined by a BET method is 700m²/g or more. When the spherical activated carbon has an SSA of lessthan 700 m²/g, an adsorbability of toxic substances is unfavorablylowered. The SSA is preferably 1300 m²/g or more, more preferably 1650m²/g or more. The upper limit of the SSA is not particularly limited,but the SSA is preferably 3000 m²/g or less in view of a bulk densityand strength.

The pore volume of the spherical activated carbon used as the adsorbentfor an oral administration of the present invention is not particularlylimited. For example, a volume of pores having a pore diameter of 20 to15000 nm is preferably 0.01 to 1 mL/g, more preferably from more than0.04 mL/g to 1 mL/g. The volume is determined by a mercurypress-injection method.

The crushing strength of the spherical activated carbon used as theadsorbent for an oral administration of the present invention ispreferably 10 N/particle or more, more preferably 25 N/particle or more,particularly preferably 30 N/particle or more. There is no upper limit,but about 80 N/particle is sufficient. When the crushing strength isless than 10 N/particle, there is a high possibility that the sphericalactivated carbon will be unfavorably fractured into powder when handledor bitten upon an oral administration. This is undesirable because it isknown that powdery activated carbon is liable to cause an interferenceof passing through an alimentary tract when orally administered, and itis preferable to maintain the spherical shape.

Properties of the spherical activated carbon used as the adsorbent foran oral administration of the present invention, namely, the averageparticle diameter, the bulk density, the specific surface area, the porevolume, the particle size distribution, and the crushing strength, aremeasured by the following methods.

(1) An Average Particle Diameter (Dv50)

A particle-sizes accumulating standard curve with respect to a volumebasis is prepared by a laser diffraction apparatus for measuringparticle size distribution [SALAD-3000S; Shimadzu Corporation]. Aparticle size at a particle-sizes accumulating ratio of 50% isdetermined as an average particle diameter (Dv50).

(2) A Bulk Density

This is measured in accordance with a method for measuring a packingdensity defined in JIS K 1474-5.7.2.

(3) A Specific Surface Area (Method for Calculating a Specific SurfaceArea by a Bet Method)

An amount of gas adsorbed is measured by a specific surface areameasuring apparatus (for example, ASAP2010 manufactured byMICROMERITICS) in accordance with a gas adsorbing method for thespherical activated carbon sample, and a specific surface area can becalculated by the following adsorption equation. More particularly, thespherical activated carbon is charged as a sample in a sample tube, anddried under a reduced pressure at 300° C. Thereafter, a weight of adried sample is measured. Then, the test tube is cooled to −196° C., andnitrogen is introduced into the test tube, whereby nitrogen is adsorbedto the spherical activated carbon sample. A relation of a nitrogenpartial pressure and an adsorbed amount (absorption-isotherm line) ismeasured.

BET plotting is carried out, given that a relative pressure of nitrogenis p, and an adsorbed amount at that time is v(cm³/g STP). That is, theplotting in a range wherein p is 0.02 to 0.20 is carried out, in thefield wherein a longitudinal axis is p/(v(1−p)), and an abscissa axis isp. Given that the gradient at that time is b(g/cm³) and an intercept isc(g/cm³), a specific surface area S (unit=m²/g) can be calculated fromthe equation:S=[MA×(6.02×10²³)]/[22414×10¹⁸×(b+c)]  [equation 3]wherein MA denotes a cross-sectional area of a nitrogen molecule, and is0.162 nm².(4) A Specific Surface Area (Method for Calculating a Specific SurfaceArea by a Langmuir's Equation)

An amount of gas adsorbed is measured by a specific surface areameasuring apparatus (for example, ASAP2010 manufactured byMICROMERITICS) in accordance with a gas adsorbing method for thespherical activated carbon sample, and a specific surface area can becalculated by Langmuir's adsorption equation. More particularly, thespherical activated carbon is charged as a sample in a sample tube, anddried under a reduced pressure at 300° C. Thereafter, a weight of adried sample is measured. Then, the test tube is cooled to −196° C., andnitrogen is introduced into the test tube, whereby nitrogen is adsorbedto the spherical activated carbon sample. A relation of a nitrogenpartial pressure and an adsorbed amount (absorption-isotherm line) ismeasured.

Langmuir's plotting is carried out, given that a relative pressure ofnitrogen is p, and an adsorbed amount at that time is v(cm³/g STP). Thatis, the plotting in a range wherein p is 0.02 to 0.20 is carried out, inthe field wherein a longitudinal axis is p/v, and an abscissa axis is p.Given that the gradient at that time is b(g/cm³), a specific surfacearea S (unit=m²/g) can be calculated from the equation:S=[MA×(6.02×10²³)]/[22414×10¹⁸ ×b]  [equation 4]wherein MA denotes a cross-sectional area of a nitrogen molecule, and is0.162 nm².(5) Pore Distribution (Calculating Equation of Horverth-Kawazoe)

A relationship between a nitrogen partial pressure and an amountadsorbed by the spherical activated carbon (absorption-isotherm line) ismeasured at a temperature of liquid nitrogen (−196° C.) by a specificsurface area measuring apparatus (ASAP2010 manufactured byMICROMERITICS), using a gas adsorption method. From the resultingabsorption-isotherm line, pore distribution is calculated by thecalculating equation of Horverth-Kawazoe [Horvath, G. and Kawazoe, K.,J. Chem. Eng. Japan 16 (6), 470 (1983)], using an analyzing softwareattached to the specific surface area measuring apparatus (ASAP2010). Inthe original calculating method of Horverth-Kawazoe, the shape of thepore is analyzed by slit geometry. In the present invention, however,the structure of carbon is three-dimensionally disordered due tonon-graphitizable carbon. Therefore, calculation according to cylindergeometry [Saito, A. and Foley, H. C., AlChE Journal 37 (3), 429 (1991)]is selected and carried out.

Parameters used in the calculation are as follows:

Interaction Parameter: 1.56×10⁻⁴³ ergs·cm⁴

Diameter of Adsorptive Molecule: 0.3000 nm

Diameter of Sample Molecule: 0.3400 nm

Density Conversion Factor: 0.001547 (cm³ liquid/cm³ STP).

(6) A Pore Volume by a Mercury Injection Method

The pore volume can be measured by a mercury porosimeter (for example,AUTOPORE 9200 manufactured by MICROMERITICS). The spherical activatedcarbon is charged as a sample in a sample vessel, and degassed under apressure of 2.67 Pa or less for 30 minutes. Then, mercury is introducedinto the sample vessel, a pressure applied is gradually increased(maximum pressure=414 MPa) to force the mercury into the micropores inthe spherical activated carbon sample. A pore volume distribution of thespherical activated carbon sample is measured from a relationshipbetween the pressure and an amount of forced mercury, by equations asmentioned below.

Specifically, a volume of mercury inserted into the spherical activatedcarbon sample while a pressure is applied is increased from a pressure(0.06 MPa) corresponding to a pore diameter of 21 μm to the maximumpressure (414 MPa) corresponding to a pore diameter of 3 nm. A porediameter can be calculated as follows. When mercury is forced into acylindrical micropore having a diameter (D) by applying a pressure (P),a surface tension (γ) of mercury is balanced with a pressure acting on asection of the micropore, and thus, a following equation is held:−nDγ cos θ=n(D/2)² ·Pwherein θ is a contact angle of mercury and a wall of the micropore.Therefore, a following equation:D=(−4γ cos θ)/Pis held.

In the present specification, the relationship between the pressure (P)and the pore diameter (D) is calculated by an equation:D=1.27/Pgiven that a surface tension of mercury is 484 dyne/cm, a contact angleof mercury and carbon is 130°, a unit of the pressure P is MPa, and aunit of the pore diameter D is μm. For example, the volume of poreshaving a pore diameter of 7.5 to 15000 nm corresponds to a volume ofmercury inserted by applying a pressure from 0.085 MPa to 169 MPa. Forexample, the volume of pores having a pore diameter of 20 to 1000 nmcorresponds to a volume of mercury inserted by applying a pressure from1.27 MPa to 63.5 MPa.

The spherical activated carbon used as the adsorbent for an oraladministration of the present invention has a very small particle size,and thus, when packed in a sample vessel, voids between sample particlesbecome small. In the process for measuring the pore volume by the abovemercury press-injection method, there is a step wherein mercury isinjected into voids between the particles under pressure. In the step,the spherical activated carbon exhibits the same behavior as if itcontains pores having a pore diameter of 8000 to 15000 nm. However, itcan be confirmed from, for example, an observation by an electronmicroscope that the spherical activated carbon used as the adsorbent foran oral administration of the present invention does not contain poreshaving a pore diameter of 8000 to 15000 nm. Therefore, an amount ofmercury injected into voids between particles under pressure is includedin the expression “volume of pores having a pore diameter of 20 to 15000nm” as used herein.

(7) Particle Size Distribution

A number-based particle distribution is measured by a laser diffractionapparatus for measuring particle size distribution [SALAD-3000S;Shimadzu Corporation] and a representative particle size D and thenumber n in a fraction of particles having particle size to be measuredare determined. A length average particle diameter D₁, and a weightaverage particle diameter D₄ are calculated by the following equations:D ₁=Σ(nD)/Σn  [equation 5]D ₄=Σ(nD ⁴)/Σ(nD ³)  [equation 6](8) Crushing Strength

A powder hardness meter [for example, simplified powder hardness metermanufactured by Tsutsui Scientific Instruments Co., Ltd.] is used tomeasure a power necessary to crush one particle of the sphericalactivated carbon sample. More particularly, one particle of thespherical activated carbon sample is held between two plates. Ifnecessary, the particle is fixed by a two-side coated adhesive tape. Apressure is applied until the sample particle is crushed and the powernecessary to crush the particle is measured.

The spherical activated carbon used as the adsorbent for an oraladministration of the present invention exhibits an excellentadsorbability of exacerbation factors of liver diseases or harmfulsubstances of renal diseases, and therefore, may be used as an adsorbentfor an oral administration for treating or preventing a renal disease ora liver disease.

As the renal disease, there may be mentioned, for example, chronic renalfailure, acute renal failure, chronic pyelonephritis, acutepyelonephritis, chronic nephritis, acute nephritic syndrome, acuteprogressive nephritic syndrome, chronic nephritic syndromes nephroticsyndrome, nephrosclerosis, interstitial nephritis, tubulopathy, lipoidnephrosis, diabetic nephropathy, renovascular hypertension, orhypertension syndrome, or secondary renal diseases caused by theseprimary diseases, or a light renal failure before a dialysis therapy,and may be used in an improvement of a light renal failure before adialysis therapy or a disease condition for a patient during a dialysistherapy (see “Clinical Nephrology”, Asakura-shoten, Nishio Honda,Kenkichi Koiso, and Kiyoshi Kurokawa, 1990; and “Nephrology”Igaku-shoin, Teruo Omae and Sei Fujimi, ed., 1981).

As the liver disease, there may be mentioned, for example, fulminanthepatitis, chronic hepatitis, viral hepatitis, alcoholic hepatitis,hepatic fibrosis, liver cirrhosis, hepatic cancer, autoimmune hepatitis,drug allergic hepatopathy, primary biliary cirrhosis, tremor,encephalopathia, dysbolism, or dysfunction. Further, the porousspherical carbonaceous substance can be used in a treatment of a diseasecaused by toxic substances in a body, such as psychosis.

Therefore, when the adsorbent for an oral administration according tothe present invention is used as an agent for treating or preventing arenal disease, it contains the spherical activated carbon as aneffective component. When the adsorbent for an oral administrationaccording to the present invention is used as an agent for a treatmentof a liver or renal disease, a dosage thereof depends on the subject(human or other animal), age, individual differences, diseaseconditions, and so on. Therefore, in some cases, a dosage outside of thefollowing dosage may be appropriate, but in general, the oral dosage inthe case of a human is usually 1 to 20 g of the adsorbent per day,wherein the daily dosage may be divided into three to four portions. Thedosage may be appropriately varied with the disease conditions. Theformulation may be administered in any form, such as powders, granules,tablets, sugar-coated tablets, capsules, suspensions, sticks, dividedpackages, or emulsions. In the case of capsules, the usual gelatincapsules, or if necessary, enteric capsules may be used. In the case oftablets, the formulations must be broken into the original fineparticles inside the body. The adsorbent may be used as a mixture withan electrolyte-controlling agent, such as an aluminum gel or Kayexalate.

The spherical activated carbon according to the present invention havingan average particle diameter of 50 to 200 μm and the bulk density ofless than 0.54 g/mL can be used as an agent for treating or preventing arenal or liver disease, in the form of a mixture with a conventionallyknown spherical activated carbon, that is, the spherical activatedcarbon or the surface-modified spherical activated carbon wherein theaverage particle diameter is outside the range of 50 to 200 μm, and/orthe bulk density is 0.54 g/mL or more. Further, the spherical activatedcarbon according to the present invention having an average particlediameter of 50 to 200 μm and the bulk density of less than 0.54 g/mL canbe used as an agent for treating or preventing a renal or liver disease,together with a conventionally known spherical activated carbon, thatis, the spherical activated carbon or the surface-modified sphericalactivated carbon wherein the average particle diameter is outside therange of 50 to 200 μm, and/or the bulk density is 0.54 g/mL or more.

EXAMPLES

The present invention now will be further illustrated by, but is by nomeans limited to, the following Examples.

Example 1

Deionized water (220 g) and methyl cellulose (58 g) were charged into a1 L separable flask. Further, 105 g of styrene, 184 g of divinyl benzenewith a purity of 57% (57% divinylbenzene and 43% ethylvinyl benzene),1.68 g of 2,2′-azobis(2,4-dimethylvaleronitrile), and 63 g of 1-butanolas a porogen were added thereto. Then, a replacement with a nitrogen gaswas carried out. The two-phase system was stirred at 200 rpm, and heatedto 55° C., and then allowed to stand for 20 hours. The resulting resinwas filtered, and dried in a rotary evaporator. In a vacuum dryer,1-butanol was removed from the resin by distillation, and the productwas dried under a reduced pressure at 90° C. for 12 hours to therebyobtain a spherical porous synthetic resin having an average particlediameter of 180 μm. A specific surface area of the porous syntheticresin was about 90 m²/g.

The resulting spherical porous synthetic resin (100 g) was charged intoa reactor having a grating, and treated to impart infusibility in avertical tubular furnace. The infusibility-imparting treatment wascarried out under the conditions that dried air (3 L/min) was upwardlypassed from the lower portion of the reactor tube, the temperature wasraised to 260° C. at a rate of 5° C./h, and the whole was allowed tostand at 260° C. for 4 hours to thereby obtain a spherical porousoxidized resin. The resulting spherical porous oxidized resin washeat-treated at 600° C. for 1 hour under a nitrogen atmosphere, and thenactivated in a fluidized bed at 820° C. for 10 hours under a nitrogengas atmosphere containing 64.5% by volume of steam, to obtain aspherical activated carbon. FIG. 1 is an electron microscope photographof the resulting spherical activated carbon. The properties of theresulting spherical activated carbon are listed in Table 1.

Example 2

The procedures of Example 1 were repeated except that the two-phasesystem was stirred at 100 rpm, instead of 200 rpm, to obtain a sphericalactivated carbon. The properties of the resulting spherical activatedcarbon are listed in Table 1.

Example 3

The procedures of Example 1 were repeated except that the two-phasesystem was stirred at 150 rpm, instead of 200 rpm, to obtain a sphericalactivated carbon. The properties of the resulting spherical activatedcarbon are listed in Table 1.

Example 4

The procedures of Example 1 were repeated except that the two-phasesystem was stirred at 300 rpm, instead of 200 rpm, to obtain a sphericalactivated carbon. The properties of the resulting spherical activatedcarbon are listed in Table 1.

Comparative Example 1

The procedures of Example 1 were repeated except that the activation wascarried out for 6 hours, instead of 10 hours, to obtain a sphericalactivated carbon. The properties of the resulting spherical activatedcarbon are listed in Table 1.

Example 5

The procedures of Example 1 were repeated except that the activation wascarried out for 13 hours, instead of 10 hours, to obtain a sphericalactivated carbon. The properties of the resulting spherical activatedcarbon are listed in Table 1.

Example 6

Petroleum pitch (680 g) (softening point=210° C.; quinoline insolublecontents=not more than 1% by weight; ratio of hydrogen atoms/carbonatoms=0.63) and naphthalene (320 g) were charged into an autoclave(internal volume=3 L) equipped with stirring fans, melted at 180° C.,and mixed. Thereafter, the mixture was cooled to 140° C. to 160° C. andextruded through a nozzle of 0.5 mm to form string-like shaped products.Then, the string-like shaped products were broken, a section having anaperture range of 100 μm to 200 μm was obtained by passing through asieve. The resulting broken products were added to an aqueous solutionprepared by dissolving 0.23% by weight of polyvinyl alcohol(saponification value=88%), and dispersed at 95° C. for 50 minutes withstirring, to thereby obtain a spheroidized product. Then, thespheroidized product was cooled to 40° C. over 90 minutes, whereby thepitch was solidified and naphthalene crystals were precipitated, and aslurry of spherical shaped products of pitch was obtained. After most ofthe water was removed by filtration, the naphthalene in the sphericalshaped products of pitch was extracted and removed with n-hexane at anamount by weight of about 6 times that of the spherical shaped productsof pitch. The resulting porous spherical pitch was heated to 235° C. bypassing a heated air in a fluidized bed, and allowed to stand at 235° C.for 1 hour, to thereby be oxidized, and a porous spherical oxidizedpitch was obtained, which was non-fusible to heat. The resulting porousspherical oxidized pitch was activated in a fluidized bed at 900° C. for174 minutes by a nitrogen gas atmosphere containing 64.5% by volume ofsteam to obtain a spherical activated carbon. The properties of theresulting spherical activated carbon are listed in Table 1.

Comparative Example 2

Petroleum pitch (68 kg) (softening point=210° C.; quinoline insolublecontents=not more than 1% by weight; ratio of hydrogen atoms/carbonatoms=0.63) and naphthalene (32 kg) were charged into an autoclave(internal volume=300 L) equipped with stirring fans, melted at 180° C.,and mixed. Thereafter, the mixture was cooled to 140° C. to 160° C. andextruded to form string-like shaped products. Then, the string-likeshaped products were broken so that a ratio of a diameter to a lengthbecame about 1 to 2. The resulting broken products were added to anaqueous solution prepared by dissolving 0.23% by weight of polyvinylalcohol (saponification value=88%) and heating to 93° C., and dispersedwith stirring to be spheroidized. Then, the whole was cooled byreplacing the polyvinyl alcohol aqueous solution with water, at 20° C.for 3 hours, whereby the pitch was solidified and naphthalene crystalswere precipitated, and a slurry of spherical shaped products of pitchwas obtained. After most of the water was removed by filtration, thenaphthalene in the spherical shaped products of pitch was extracted andremoved with n-hexane at an amount by weight of about 6 times that ofthe spherical shaped products of pitch. The resulting porous sphericalpitch was heated to 235° C. by passing a heated air in a fluidized bed,and allowed to stand at 235° C. for 1 hour, to thereby be oxidized, anda porous spherical oxidized pitch was obtained, which was non-fusible toheat. Thereafter, the resulting porous spherical oxidized pitch wasactivated in a fluidized bed at 820° C. for 400 minutes by a nitrogengas atmosphere containing 64.5% by volume of steam to obtain a sphericalactivated carbon. The properties of the resulting spherical activatedcarbon are listed in Table 1.

Comparative Example 3

The spherical activated carbon obtained in Comparative Example 2 wasfurther oxidized in the fluidized bed at 470° C. for 195 minutes under anitrogen-oxygen atmosphere containing 18.5% by volume of oxygen, andreduced in the fluidized bed at 900° C. for 17 minutes under a nitrogengas atmosphere to obtain a surface-modified spherical activated carbon.The properties of the resulting surface-modified spherical activatedcarbon are listed in Table 1.

Comparative Example 4

The procedures of Example 1 were repeated except that the two-phasesystem was stirred at 80 rpm, instead of 200 rpm, to obtain a sphericalactivated carbon. The properties of the resulting spherical activatedcarbon are listed in Table 1.

Comparative Example 5

The procedures of Example 1 were repeated except that the sphericalactivated carbon obtained by the activation treatment in Example 1 wasground for 10 seconds in a rod mill, to obtain a activated carbon. Theproperties of the resulting activated carbon are listed in Table 1.

Example 7

Deionized water (3003 g) and 1.4% methyl cellulose aqueous solution (530g) were charged into a 10 L stainless steel polymerizing vessel.Further, 813 g of styrene, 1427 g of divinyl benzene with a purity of57% (57% divinylbenzene and 43% ethylvinyl benzene), 13 g of2,2′-azobis(2,4-dimethylvaleronitrile), and 634 g of 1-butanol as aporogen were added thereto. Then, a replacement with a nitrogen gas wascarried out. The two-phase system was stirred at 220 rpm, and heated to55° C., and then allowed to stand for 20 hours. The resulting resin wasfiltered, and dried in a rotary evaporator. In a vacuum dryer, 1-butanolwas removed from the resin by distillation, and the product was driedunder a reduced pressure at 90° C. for 12 hours to thereby obtain aspherical porous synthetic resin having an average particle diameter of200 μm. A specific surface area of the porous synthetic resin was about100 m²/g.

The resulting spherical porous synthetic resin (100 g) was charged intoa reactor having a grating, and treated to impart infusibility in avertical tubular furnace. The infusibility-imparting treatment wascarried out under the conditions that dried air (3 L/min) was upwardlypassed from the lower portion of the reactor tube, the temperature wasraised to 260° C. at a rate of 5° C./h, and the whole was allowed tostand at 260° C. for 4 hours. The resulting spherical porous oxidizedresin was heat-treated at 600° C. for 1 hour under a nitrogenatmosphere, and then activated in a fluidized bed at 820° C. for 13.5hours under a nitrogen gas atmosphere containing 64.5% by volume ofsteam, to obtain a spherical activated carbon. The properties of theresulting spherical activated carbon are listed in Table 2.

Example 8

The procedures of Example 7 were repeated except that the activation wascarried out for 11.5 hours, instead of 13.5 hours, at 820° C., to obtaina spherical activated carbon. The properties of the resulting sphericalactivated carbon are listed in Table 2.

Example 9

The procedures of Example 7 were repeated except that the activation wascarried out for 9 hours, instead of 13.5 hours, at 820° C., to obtain aspherical activated carbon. The properties of the resulting sphericalactivated carbon are listed in Table 2.

Example 10

The procedures of Example 8 were repeated except that the two-phasesystem was stirred at 150 rpm, instead of 200 rpm, to obtain asurface-modified spherical activated carbon. The properties of theresulting spherical activated carbon are listed in Table 2.

Comparative Example 6

The procedures of Example 7 were repeated except that the activation wascarried out for 6 hours, instead of 13.5 hours at 820° C., to obtain asurface-modified spherical activated carbon. The properties of theresulting surface-modified spherical activated carbon are listed inTable 2.

Comparative Example 7

The procedures of Example 7 were repeated except that the activation wascarried out for 5 hours, instead of 13.5 hours at 820° C., to obtain asurface-modified spherical activated carbon. The properties of theresulting surface-modified spherical activated carbon are listed inTable 2.

Comparative Example 8

The procedures of Example 8 were repeated except that the two-phasesystem was stirred at 75 rpm, instead of 200 rpm, to obtain asurface-modified spherical activated carbon. The properties of theresulting spherical activated carbon are listed in Table 2.

Comparative Example 9

Spherical phenolic resin (“Maririn” HF500; Gun Ei Chemical Industry Co.,Ltd.) was sieved through a screen to remove fine powders. Then, 150 g ofthe resulting spherical phenolic resin was charged into a verticalreaction quartz tube having a grating, and maintained at 700° C. for 1hour. After allowing to stand for cooling, the whole was washed withdeionized water, and dried to obtain a spherical carbonaceous material.The resulting spherical carbonaceous material was activated at 820° C.for 6 hours in a fluidized bed at a nitrogen gas atmosphere containing64.5% by volume of steam, to thereby obtain a spherical activatedcarbon. The properties of the resulting spherical activated carbon arelisted in Table 2.

[Method for Evaluation of the Oral Adsorbents]

The properties shown in the following Tables 1 and 2 were measured bythe following methods.

(1) Average Particle Diameter

The laser diffraction apparatus for measuring particle size distributionas mentioned above was used for the measuring.

(2) Pore Volume

The surface-modified spherical activated carbon or the sphericalactivated carbon prepared in Examples and Comparative Examples wasmeasured by the mercury injection method as mentioned above.

(3) Specific Surface Area by Bet or Langmuir's Method

The BET or Langmuir's method as mentioned above was used for themeasuring.

(4) Bulk Density

The sample was charged into a 50 mL graduated measuring cylinder untilthe sample reached a scale of 50 mL. After the cylinder was tapped 50times, a weight of the sample was divided by a volume of the sample tofind a bulk density. The results are shown in Tables 1 and 2. It wasconfirmed that the results obtained by the above method were equal tothose obtained by the method for determining a packing density inaccordance with JIS K 1474-5.7.2 in the range of the significant figuresshown in Tables 1 and 2.

(5) Crushing Strength

A powder hardness meter [for example, simplified powder hardness metermanufactured by Tsutsui Scientific Instruments Co., Ltd.] is used tomeasure a power necessary to crush one particle of the sphericalactivated carbon sample. More particularly, one particle of thespherical activated carbon sample is held between two plates. Ifnecessary, the particle is fixed by a two-side coated adhesive tape. Apressure is applied until the sample particle is crushed and the powernecessary to crush the particle is measured. The larger the particlesize, the larger the crushing strength. Therefore, when the strength ofthe particle having an average particle diameter Dv50 of 200 μm or morewas measured, the sample clogged on a sieve having an aperture of 425 μmwas used. When the strength of the particle having an average particlediameter Dv50 of 200 μm or less was measured, the sample having aparticle diameter of 75 μm to 180 μm was obtained by sieving and thecrushing strength thereof was measured. The measuring procedures werecarried out 20 times, and the average thereof was recorded as thecrushing strength.

(6) Adsorption Test of α-Amylase

The spherical activated carbon sample or the surface-modified sphericalactivated carbon sample was dried, and 0.500 g of the dried sample wasaccurately weighed and charged into a conical flask equipped with aground-in stopper. On the other hand, 0.100 g of α-amylase (liquefiedtype) was accurately weighed and dissolved by adding a phosphate buffer(pH 7.4) to prepare a stock solution having an accurate volume of 1000mL. The stock solution in an accurate amount of 50 mL was charged to theconical flask equipped with a ground-in stopper. The flask was shaken at37±1° C. for 3 hours. The product in the flask was filtered with suctionthrough a 0.65 μmembrane filter. A first filtrate (about 20 mL) wasdiscarded, and a subsequent filtrate (about 10 mL) was taken as a samplesolution.

Further, the same procedures were repeated except that only a phosphatebuffer (pH 7.4) was used, to obtain a filtrate as a correction solution.The sample solution and the correction solution were analyzed by anabsorptiometeric analysis, using a phosphate buffer (pH 7.4) as acontrol. The absorbance at a wavelength of 282 nm was measured. Adifference between the absorbance of the sample solution and theabsorbance of the correction solution was taken as a test absorbance.

A standard curve was prepared by adding the α-amylase stock solution inan accurate amount of 0 mL, 25 mL, 50 mL, 75 mL, or 100 mL to ameasuring flask, adding a phosphate buffer (pH 7.4) to 100 mL, andmeasuring an absorbance at a wavelength of 282 nm. From the testabsorbance and the standard curve, an amount (mg/dL) of α-amylaseadsorbed in the solution was calculated. The results are shown in Tables1 and 2.

(7) Adsorption Test of Indole

An adsorption test of indole for the spherical activated carbon or thesurface-modified activated carbon prepared in Examples 1 to 12 orComparative Examples 1 to 11 was carried out, as follows.

The spherical activated carbon sample or the surface-modified sphericalactivated carbon sample was dried, and 0.01 g of the dried sample wasaccurately weighed and charged into a conical flask equipped with aground-in stopper. 50 mL of an indole aqueous solution (indoleconcentration=100 mg/L) prepared by dissolving indole by adding aphosphate buffer (pH 7.4) was charged to the conical flask equipped witha ground-in stopper. The flask was shaken at 40° C. for 3 hours by ashaker. The product in the flask was filtered. The resulting filtratewas analyzed by an ultraviolet adsorption (265 nm) to measure a residualamount of indole, and calculate an amount of indole adsorbed. Theresults are shown in Tables 1 and 2.

(8) Change in an Adsorbed Amount of Indole with Time

In the above-mentioned test (7), “Adsorption test of indole”, thespherical activated carbon sample was brought into contact with andshaken with indole for a predetermined period of time, i.e., for 3hours. On the contrary, in the present test, the shaking time was variedand a change of an adsorption rate was measured for the sphericalactivated carbon prepared in Example 1, Comparative Example 1 orComparative Example 2.

The amounts of indole adsorbed were determined according to the methodmentioned in the above item (6) when the shaking time was 3 hours, 5hours, or 24 hours. The results are shown in FIG. 2.

(9) Relationship Between an Average Particle Diameter and an Amount ofIndole Adsorbed

According to the method described in the above-mentioned test (7),“Adsorption test of indole”, an amount of indole adsorbed was measuredfor the spherical activated carbon having various average particlediameters to examine the relationship between an average particlediameter and an amount of indole adsorbed. The results are shown in FIG.3. It was found that an excellent adsorbability of indole was observedin a range of 50 to 200 μm of an average particle diameter.

(10) Adsorption Test of Tryptophan

An adsorption test of tryptophan for the spherical activated carbon orthe surface-modified spherical activated carbon prepared in Examples 7to 12 or Comparative Examples 6 to 11 was carried out, as follows.

The spherical activated carbon sample or the surface-modified sphericalactivated carbon sample was dried, and 0.01 g of the dried sample wasaccurately weighed and charged into a conical flask equipped with aground-in stopper. 50 mL of a tryptophan aqueous solution (tryptophanconcentration=100 mg/L) prepared by dissolving tryptophan by adding aphosphate buffer (pH 7.4) was charged to the conical flask equipped witha ground-in stopper. The flask was shaken at 40° C. for 3 hours by ashaker. The product in the flask was filtered. The resulting filtratewas analyzed by an ultraviolet adsorption (280 nm) to calculate anamount of tryptophan adsorbed. The results are shown in Table 2. TABLE 1Volume of Specific pores with Average particle surface area porediameter Langmuir BET Bulk diameter of Dv50 Length D₁ Weight D₄ methodmethod density 20-15000 nm (μm) (μm) (μm) D₄/D₁ (m²/g) (m²/g) (g/mL)(mL/g) Example 1 Cross-linked 117 118 133 1.12 2407 1906 0.50 0.06 vinylresin Example 2 Cross-linked 198 168 196 1.16 2451 1978 0.50 0.05 vinylresin Example 3 Cross-linked 150 142 156 1.09 2380 1921 0.50 0.06 vinylresin Example 4 Cross-linked 70 67 74 1.11 2422 1955 0.50 0.11 vinylresin Example 5 Cross-linked 117 128 132 1.03 2715 2210 0.47 0.08 vinylresin Example 6 Pitch 94 88 109 1.23 2252 1853 0.50 0.15 ComparativeCross-linked 119 119 135 1.14 1443 1177 0.63 0.03 Example 1 vinyl resinComparative Pitch 447 473 507 1.07 2236 1801 0.50 0.08 Example 2Comparative Pitch 350 374 398 1.06 2205 1537 0.50 0.06 Example 3Comparative Cross-linked 283 288 326 1.13 2218 1525 0.50 0.03 Example 4vinyl resin Comparative Cross-linked 40 13 49 3.8 2320 1541 0.50 0.41Example 5 vinyl resin Adsorption amount of α- amylase Amount of Amountof (residual Acidic Crushing indole tryptophan amount after pointsstrength adsorbed adsorbed adsorption) (meq/g) (N/particle) (mg/g)(mg/mL) (mg/g) (mg/dL) Example 1 0.18 >40 430 215 2.04 (7.96) Example 20.16 >40 395 198 1.87 (8.13) Example 3 0.18 >40 402 201 1.80 (8.20)Example 4 0.20 >40 441 221 355 2.20 (7.80) Example 5 0.23 >40 480 2262.28 (7.72) Example 6 0.21 2.3 420 210 281 3.42 (6.58) Comparative0.19 >40 315 198 1.79 (8.21) Example 1 Comparative 0.19 2.0 330 165 1512.32 (7.68) Example 2 Comparative 0.67 2.0 270 135 2.81 (7.19) Example 3Comparative 0.17 >40 310 155 1.49 (8.51) Example 4 Comparative 0.20unmeasurable 445 223 375 4.88 (5.12) Example 5

TABLE 2 Volume of Volume of pores with pores with pore pore AverageSpecific diameter diameter Crush- Ad- particle surface area of of ingAmount Amount of sorption diameter Langmuir BET Bulk 20-1000 20-15000Acidic strength of indole tryptophan amount of Starting Dv50 methodmethod density nm nm points (N/ adsorbed adsorbed α-amylase material(μm) (m²/g) (m²/g) (g/mL) (mL/g) (mL/g) (meq/g) particle) (mg/g) (mg/g)(mg/g) Example 7 Cross-linked 101 2760 2250 0.47 0.04 0.07 0.18 >40 390321 1.9 vinyl resin Example 8 Cross-linked 103 2520 2050 0.49 0.03 0.060.18 >40 378 318 1.7 vinyl resin Example 9 Cross-linked 103 2070 16800.53 0.03 0.06 0.17 >40 365 307 1.6 vinyl resin Example 10 Cross-linked150 2530 2030 0.49 0.03 0.05 0.17 >40 323 253 1.6 vinyl resinComparative Cross-linked 105 1440 1180 0.60 0.02 0.03 0.17 >40 347 1791.5 Example 6 vinyl resin Comparative Cross-linked 105 1350 1080 0.620.01 0.03 0.16 >40 343 75 1.5 Example 7 vinyl resin ComparativeCross-linked 345 2510 2030 0.49 0.04 0.02 0.19 >40 261 165 1.3 Example 8vinyl resin Comparative Phenol resin 330 1650 1330 0.60 0.01 0.02 0.3122 210 69 1.3 Example 9

INDUSTRIAL APPLICABILITY

The adsorbent for an oral administration according to the presentinvention can be used as an adsorbent for an oral administration fortreating or preventing a renal disease, or an adsorbent for treating orpreventing a liver disease.

As the renal disease, there may be mentioned, for example, chronic renalfailure, acute renal failure, chronic pyelonephritis, acutepyelonephritis, chronic nephritis, acute nephritic syndrome, acuteprogressive nephritic syndrome, chronic nephritic syndromes nephroticsyndrome, nephrosclerosis, interstitial nephritis, tubulopathy, lipoidnephrosis, diabetic nephropathy, renovascular hypertension, orhypertension syndrome, or secondary renal diseases caused by theseprimary diseases, or a light renal failure before a dialysis therapy,and may be used in an improvement of a light renal failure before adialysis therapy or a disease condition for a patient during dialysistherapy (see “Clinical Nephrology”, Asakura-shoten, Nishio Honda,Kenkichi Koiso, and Kiyoshi Kurokawa, 1990; and “Nephrology”Igaku-shoin, Teruo Omae and Sei Fujimi, ed., 1981).

As the liver disease, there may be mentioned, for example, fulminanthepatitis, chronic hepatitis, viral hepatitis, alcoholic hepatitis,hepatic fibrosis, liver cirrhosis, hepatic cancer, autoimmune hepatitis,drug allergic hepatopathy, primary biliary cirrhosis, tremor,encephalopathia, dysbolism, or dysfunction. Further, the porousspherical carbonaceous substance can be used in a treatment of a diseasecaused by toxic substances in a body, such as psychosis.

Although the present invention has been described with reference tospecific embodiments, various changes and modifications obvious to thoseskilled in the art are possible without departing from the scope of theappended claims.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. An adsorbent for an oraladministration, comprising a spherical activated carbon wherein anaverage particle diameter is 50 to 200 μm, and a specific surface areadetermined by a BET method is 700 m²/g or more.
 5. The adsorbentaccording to claim 4, wherein a ratio (D₄/D₁) of a weight averageparticle diameter (D₄) of a weight-based-distribution to a lengthaverage particle diameter (D₁) of a number-based-average is 3 or less.6. The adsorbent according to claim 4, wherein the spherical activatedcarbon is prepared from cross-linked vinyl resin, ion-exchanged resin,or pitch as a carbon source.
 7. The adsorbent according to claim 4,wherein the spherical activated carbon is prepared from a sphericalheat-fusible resin which has been treated to impart infusibility.
 9. Anagent for treating or preventing a renal disease, comprising theadsorbent for an oral administration according to claim 4 as aneffective component.
 10. An agent for treating or preventing a liverdisease, comprising the adsorbent for an oral administration accordingto claim 4 as an effective component.
 11. An adsorbent for an oraladministration, comprising a spherical activated carbon wherein anaverage particle diameter is 50 to 200 μm, a specific surface areadetermined by a BET method is 700 m²/g or more, and a bulk density isless than 0.54 g/mL.
 12. The adsorbent according to claim 11, wherein aratio (D₄/D₁) of a weight average particle diameter (D₄) of aweight-based-distribution to a length average particle diameter (D₁) ofa number-based-average is 3 or less.
 13. The adsorbent according toclaim 11, wherein the spherical activated carbon is prepared fromcross-linked vinyl resin, ion-exchanged resin, or pitch as a carbonsource.
 14. The adsorbent according to claim 11, wherein the sphericalactivated carbon is prepared from a spherical heat-fusible resin whichhas been treated to impart infusibility.
 15. An agent for treating orpreventing a renal disease, comprising the adsorbent for an oraladministration according to claim 11 as an effective component.
 16. Anagent for treating or preventing a liver disease, comprising theadsorbent for an oral administration according to claim 11 as aneffective component.